Field of Invention
The present invention relates to a method for controlling wave and a circuit. More particularly, the present invention relates to a method for controlling modulation wave and a three-phase three-wire three-level circuit.
Description of Related Art
With development of power electronics technology, converters using semiconductor switching devices have been widely used in industry, wherein the application of the on/off-grid three-phase three-wire converter becomes more and more, such as the inverter, the rectifier, and the Static Var Generator (SVG).
In the aforementioned circuits, the semiconductor switching devices, such as the Insulated Gate Bipolar Transistor (IGBT), the Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), and the SiC MOSFET, are used therein. When the circuit operates, the semiconductor switching device therein will produce switching loss and conduction loss. The aforementioned switching loss is related to the characteristics, the driving circuit, the DC voltage, the flowing current, and the switching frequency of the semiconductor switching device; and the conduction loss is related to the characteristics and the flowing current of the semiconductor switching device.
At this stage, in order to pursue targets, for example, the high power density and reducing the volume of filters, the higher switching frequency is usually adopted. However, once the switching frequency is raised, the switching loss of the semiconductor switching device will be increased correspondingly. If the switching loss is too large, the operating temperature and the system efficiency of the semiconductor switching device will be affected directly.
It can be seen that, in the existing ways which mention above, inconvenience and defect apparently still exists, and it is necessary to be improved. In order to solve the above problems, related fields made a great effort to seek the solutions, but it did not develop the appropriate solutions for so long.